1. Field of the Invention
The present invention relates to a flexible substrate, such as a TAB tape, to be used for assemblage of a semiconductor chip such as for example, a microprocessor and a metallic mold to be used for resin-molding a semiconductor chip mounted to the flexible substrate.
2. Description of the Related Art
A TAB (Tape Automated Bonding) technique is one of the mounting techniques of an IC chip. This TAB technique has an advantage, for example, in that it permits to form leads with more multiple pins and narrower pitch, as compared with other mounting techniques, and the high speed automatic bonding can be performed in the face-up mode. Therefore, the TAB technique has recently attracted special attention.
FIG. 11 is a schematic plan view showing the construction of a typical TAB tape which is generally used. FIG. 12 is a schematic sectional view, viewed from the line D--D of FIG. 11, showing a state in which the TAB tape shown in FIG. 11 is held in a metallic mold for resin molding.
The TAB tape shown in FIG. 11 includes an IC chip 132, and a film carrier in which leads 136 are formed on a film 134. The IC chip 132 is bonded to the leads 136 through respective bumps (not shown). In the film 134, there are formed a device hole 133 to which the IC chip 132 is mounted, and two kinds of punch holes 142 and 144. The groups of leads 136a through 136d are, as shown in FIG. 11, extracted in four directions, that is, upward, downward, right-ward and left-ward. Moreover, a portion surrounded by a dashed line in FIG. 11 is an area to be resin-molded, and the portions of the tape to be resin-molded are supported by supporting portions 146.
Then, in order to resin-mold the IC chip 134 for protection of the IC chip 132, the transfer mold method is mainly used. The transfer mold method is a method wherein, as shown in FIG. 12, the TAB tape having the IC chip 132 mounted thereon is held in a metallic mold for resin-molding including an upper metallic mold 102 and a lower metallic mold 104 and a resin melted by heat is injected under pressure into a resin injection cavity 114 defined between the upper and lower metallic molds 102 and 104 and solidified. This method is advantageous in that if the injection of the melted resin into the metallic mold for resin molding is performed at a low rate, it is possible to massproduce resin-molded ICs having constant quality without deteriorating the characteristics of the IC chips and the like.
However, when the leads formed on the flexible tape, such as the TAB tape, are gripped by the metallic mold for resin molding, gaps are produced between the adjacent leads since each lead has a thickness. Generally, the resin can flow into a gap having a width of 50 .mu.m. Accordingly, when the melted resin is injected into the cavity in the metallic mold for resin molding, the resin flows into gaps between the adjacent leads so that burrs are produced between the adjacent leads much or less depending on the thickness of the leads. Therefore, there arises a problem in that when the resin-molded TAB tape is punched, the leads are deformed or cut due to the presence of the burrs. On the other hand, in a method described in JP-A-1-183837 (1989), the TAB tape is pressed at its upper and lower sides by the metallic mold for package to forcedly deform the tape by the pressure, whereby the gaps between the leads and the tape are closed to prevent the leakage of the resin. Generally, the leakage of the resin is prevented. However, there is a possibility that due to the pressing pressure of the metallic mold required for closing the gaps between the leads and the tape, the leads are deformed which degrades the conductivity.
Moreover, as described in U.S. Pat. No. 3,689,991 and U.S. Pat. No. 5,031,022, there is known a method in which the shape of the lead is so designed that the leakage of the resin is prevented. In such a case, however there arises a problem in that since the gaps are produced at portions where no lead is extracted (the same as the supporting portions 16 of FIG. 11), between the upper metallic mold and the film correspondingly to the thickness of the lead, the leakage of the resin may occur at those portions to produce burrs.
The present invention has been made on the basis of the above circumstance and it is an object of the invention to provide a flexible substrate to be used for assemblage of a semiconductor chip and capable of preventing burrs from being produced when performing the resin molding and to provide a metallic mold to be used for resin-molding the semiconductor chip mounted to the flexible substrate.